This invention relates to the field of exposure control systems.
Numerous systems are known for selectively controlling the exposure interval of a camera shutter. Most of these systems are essentially analog in nature wherein comparators compare the signal proportional to the illumination intensity with a changing analog reference signal often produced by an "RC" circuit. The beginning of the exposure interval is initiated by changing the charge in a capacitor and the end of the interval occurs when the above-mentioned comparison occurs. Since these systems are essentially analog in character, variations in the component parameters such as capacitance and resistance produce inaccuracies in the desired exposure intervals. Voltage fluctuations associated with the power supplies employed therein, and noise variations, and leaky capacitors also produce errors.
Accordingly, it is highly desirable to produce an inexpensive, stable, and accurate essentially digital shutter exposure control system.